The Wnt genes are a family of secreted signaling molecules that have been implicated in oncogenesis and development. The Drosophila homolog of mouse Wnt-1, wingless (wg), was initially identified as a gene involved in adult wing development. Subsequently, genetic screens have identified alleles of wg that cause lethality during embryonic development. Analysis of wg function during embryonic as well as imaginal development have demonstrated that Wg is involved in multiple developmental events. These include embryonic segmentation, midgut patterning, patterning of the wing margin and specification of ventral cell fates in the imaginal discs. Biochemical approaches designed to determine the molecular events associated with Wg signaling have yielded little information. Indeed, most of the current knowledge of the mechanism by which Wnt proteins operate has come out from genetic analysis conducted in Drosophila on Wg signaling. To date four genes, porcupine (porc), dishevelled (dsh), zeste white 3/shaggy (zw3) and armadillo (arm), involved in wg signaling have been identified genetically. The goal of this proposal is to characterize two new components of this pathway that have been identified from genetic screens for novel maternal effect mutants. These analyses will lead to a better understanding of the molecular events involved in Wg signal transduction and as a result should provide additional insights into Wnt signaling.